根据条件批量拆分ArrayList的流式接口
根据条件批量拆分ArrayList的流式接口
提问于 2021-10-15 19:12:34
给定以下示例种子：
List<EmailGroupingDataDTO> emailDataToGroup = Arrays.asList(
buildEmailGroupingDto(1L, "member_number_1", "username_1", "group_code_1"),
buildEmailGroupingDto(2L, "member_number_1", "username_1", "group_code_1"),
buildEmailGroupingDto(3L, "member_number_1", "username_2", "group_code_1"),
buildEmailGroupingDto(4L, "member_number_1", "username_2", "group_code_1"),
buildEmailGroupingDto(5L, "member_number_1", "username_2", "group_code_3"),
buildEmailGroupingDto(6L, "member_number_2", "username_1", "group_code_1"),
buildEmailGroupingDto(7L, "member_number_2", "username_1", "group_code_2"),
buildEmailGroupingDto(8L, "member_number_2", "username_1", "group_code_2"),
buildEmailGroupingDto(9L, "member_number_3", "username_1", "group_code_1"),
buildEmailGroupingDto(10L, "member_number_3", "username_1", "group_code_1"),
buildEmailGroupingDto(11L, "member_number_3", "username_1", "group_code_2"),
buildEmailGroupingDto(12L, "member_number_3", "username_1", "group_code_2"),
buildEmailGroupingDto(13L, "member_number_3", "username_1", "group_code_3"),
buildEmailGroupingDto(14L, "member_number_4", "username_1", "group_code_3"),
buildEmailGroupingDto(15L, "member_number_4", "username_1", "group_code_3")
);我想创建一个列表(批)列表，基于迭代列表时以下属性之一是否发生更改：
private boolean isEmailDataEqual(EmailGroupingDataDTO currDto, EmailGroupingDataDTO nextDto) {
return currDto.getMemberNumber().equals(nextDto.getMemberNumber())
&& currDto.getUsername().equals(nextDto.getGroupCode())
&& currDto.getGroupCode().equals(nextDto.getGroupCode());
}通过定期迭代，我可能可以自己管理这一点。
然而，我的问题是，是否有一个流api可以声明性地管理这一点。
回答 2
Stack Overflow用户
发布于 2021-10-15 20:24:14
StreamEx将为您完成以下操作：
List<List<EmailGroupingDataDTO>> groups = StreamEx.of(emailDataToGroup)
.groupRuns(this::isEmailDataEqual)
.toList();Stack Overflow用户
发布于 2021-10-15 21:42:46
您可以使用AtomicInteger & AtomicReference作为Collectors.groupingBy的分类器，并构建一个映射(并使用Map.values获取分组的批次)。整数作为组键，引用作为组的代表性元素，并为您的属性提供一种简单的比较方法。
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
....
List<EmailGroupingDataDTO> emailDataToGroup = //your list
AtomicInteger ai = new AtomicInteger();
AtomicReference<EmailGroupingDataDTO> myRef = new AtomicReference<>(emailDataToGroup.get(0));
Collection<List<EmailGroupingDataDTO>> result =
emailDataToGroup.stream().collect(Collectors.groupingBy(myDto -> {
boolean equal = isEmailDataEqual(myDto, myRef.get());
if (!equal) myRef.getAndSet(myDto);
return equal ? ai.get() : ai.incrementAndGet();
})).values();注意:正如@所指出的那样，这种方法只有在你按顺序排列列表的情况下才会起作用。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/69589568
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